Re: [PATCH 2 of 4] Introduce i386 fibril scheduling

[Ingo Molnar <mingo@elte.hu>]

* Zach Brown <zach.brown@oracle.com> wrote:

> This patch introduces the notion of a 'fibril'.  It's meant to be a 
> lighter kernel thread. [...]

as per my other email, i dont really like this concept. This is the 
killer:

> [...]  There can be multiple of them in the process of executing for a 
> given task_struct, but only one can every be actively running at a 
> time. [...]

there's almost no scheduling cost from being able to arbitrarily 
schedule a kernel thread - but there are /huge/ benefits in it.

would it be hard to redo your AIO patches based on a pool of plain 
simple kernel threads?

We could even extend the scheduling properties of kernel threads so that 
they could also be 'companion threads' of any given user-space task. 
(i.e. they'd always schedule on the same CPu as that user-space task)

I bet most of the real benefit would come from co-scheduling them on the 
same CPU. But this should be a performance property, not a basic design 
property. (And i also think that having a limited per-CPU pool of AIO 
threads works better than having a per-user-thread pool - but again this 
is a detail that can be easily changed, not a fundamental design 
property.)

	Ingo
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/